DESCRIPTION: (adapted from the abstract) Histamine has long been thought to play a role in the control of skeletal muscle blood flow and adrenergic systems have been implicated in this role, however, the effects of histamine on skeletal muscle blood vessels have rarely been investigated in vitro. The general aims of this study are: 1) to understand histamine-mediated mechanisms which contribute to the regulation of vascular tone in skeletal muscle (vastus intermedius and lateralis) arteries; 2) to determine if and how they interact with adrenergic mechanisms; and 3) to discover if differences exist in these mechanisms which relate to the variation in oxidative capacity found among skeletal muscles. Vascular tension development in response to electrical field stimulation, mast cell degranulation, and the application of specific agonist and antagonists to histamine and catecholamines will be measured in vitro using large and small blood vessel myograph techniques. The responses of vastus intermedius and vastus lateralis arteries before and after drug treatment will be compared using paired T analysis. This study will enhance our understanding by identifying histaminergic mechanisms which contribute to control of vascular tone in skeletal muscle and which may be responsible for variations within the skeletal muscle bed.